Some 5 per cent of respondents agreed with the statement “I have a lot of sympathy with young Muslims who leave the UK to join fighters in Syria”, and 14 per cent said they had some sympathy.

The Sun has been accused of misrepresenting these statistics and Survation has distanced itself from the reporting.

Survation chief executive Damian Lyons Lowe told The Guardian: “Survation do not endorse or support the way in which this poll’s findings have been presented by the Sun newspaper and others. Neither the headline nor the body text of any articles published were shared with or approved by Survation prior to publication.”

The newspaper quotes Ben Page, chief executive of polling company Ipsos Mori, as saying: “The main issue with this poll is the reporting, which made it appear that one in five of those sampled supported Isis, when in fact they were expressing sympathy with people going to fight in Syria, as I understand it, which could of course include British ex-servicemen fighting against Isis with the Kurds, or anti-Assad Muslim forces who are also fighting against Isis.”

The Sun said in a statement: “We are surprised at the comments from Survation, who undertook the polling for the Sun newspaper. The questions were discussed in full and agreed with them in advance, and the question about ‘sympathy’ was specifically written and suggested by them.

“In any event, it is not for a polling company to endorse or otherwise the editorial interpretation of a survey. The Sun published the poll's findings clearly and accurately, including the questions in full.

“The spread inside the newspaper reported other newsworthy lines from the survey, including the percentage of British Muslims who support action in Syria and how British Muslims choose to identify themselves. We also made clear that the number of British Muslims who had sympathy or support for IS was lower than a similar survey by Sky News conducted in March.

“The fact remains that a significant minority of Muslims have sympathy for the actions of extremists. That is a subject worthy of discussion and The Sun believes that it must be appropriate for that conversation to take place.”

This story has become the most complained about since press regulator IPSO replaced the Press Complaints Commission in September 2014.